(1) Field of the Invention
The present invention relates to flow control systems and in particular, to a flow control system having an actuated elastomeric membrane that is deformed or displaced in order to control the flow of a fluid against the elastomeric membrane.
(2) Description of the Prior Art
Turbulent fluid flow against a surface often causes drag or radiated noise due to forces from the boundary layer of the flowing fluid acting on the proximate surface. One area in which turbulent fluid flow is of particular concern is at the surface of an underwater vehicle or vessel where hydrodynamic drag and hydroacoustic radiated noise is undesirable. In the typical boundary layer fluid flow, the fluid velocity at the surface relative to the object or body approaches zero. Moving outwardly from the surface of the object or body, the time-averaged fluid velocity gradually approaches that of the ambient fluid. The instantaneous turbulent velocity profile, however, can be very complicated.
Some attempts have been made at controlling this boundary layer fluid flow, for example, using passive and active compliant coatings, magnetohydrodynamic devices, introduction of polymers, introducing fluid, applying suction, and heating. Such techniques have had limited effectiveness at reducing drag and radiated noise at the surface. The effect of active compliant coatings acting through motion which is primarily normal to the surface of the coating has also been limited. Providing motion normal to the surface with an active compliant coating often causes undesirable effects associated with disturbances to the local pressure field, for example, local adverse pressure gradients. Passive compliant coatings and other passive techniques for controlling flow are even less effective in controlling or altering the boundary layer flow.